The following relates to the lighting arts, and to light emitting packages based on one or more light emitting chips and to methods for making same.
Light emitting packages based on light emitting chips, such as semiconductor light emitting diode chips, organic light emitting diode chips, semiconductor laser chips, and so forth, are increasingly used for illumination. Each chip typically produces radiation that is saturated light at a single color point, such as red light, green light, blue light, or so forth, or violet or ultraviolet light over a narrow spectral range. It is known to operatively couple the chip with a wavelength converting phosphor so as to produce a desired light output such as an approximate white light output. Additionally, the chip typically emits incoherent and unfocused radiation. (An exception are laser diode chips, which may produce coherent and directional radiation.) It is further known to couple the LED (optionally coated with phosphor) with a focusing lens. For example, the lens may be a molded encapsulant shaped into a desired lensing configuration, or may be a separately fabricated “microlens” that is positioned over and in optical communication with the chip. Still further, in view of the limited light output provided by a single chip, it is known to use an array or combination of chips.
Existing light emitting packages have been less than fully satisfactory. Soft molded encapsulants, for example, are typically prone to damage due to abrasion, exposure to corrosive chemicals, or so forth. Separately fabricated microlenses can be more robust, but require careful placement over the chip. Moreover, for illumination it is typically not desired to focus the light.
Multiple chip packages provide greater illumination, but generally increase package complexity. Some example multiple chip packages are disclosed in Lowery, U.S. Pat. No. 6,504,301, which shows various arrangements involving generally wire-bonded interconnection of a plurality of light emitting dice disposed on a support placed in a housing including a cylindrical casing and a fluorescent plate. Other example multiple chip packages are disclosed in Baretz et al., U.S. Pat. No. 6,660,175. Baretz discloses a phosphor contained in an encapsulant disposed inside the housing, The complexity of multiple chip packages such as those of Lowery and Baretz can adversely impact manufacturability, reliability, and manufacturing costs.